Maternal ethanol consumption has been and remains a significant public health concern for the wellbeing of the progeny. Preventable as it is by abstinence during pregnancy, and despite public outreach and awareness, a significant percentage of women continue to drink during pregnancy, some even binge drink to risky levels. Consumption of ethanol during pregnancy can lead to fetal alcohol spectrum disorders (FASD), hallmarked by life- long neurobehavioral and cognitive abnormalities in the offspring. Ethanol readily crosses the placenta, and children with history of having been exposed in utero to even moderate levels of ethanol frequently present with varying degrees of deleterious neurobehavioral and cognitive outcomes. Yet, effective targeted treatment strategies for FASD/FAS are lacking or at best ill defined. The overarching contention driving this research project is that a better understanding of the cellular and molecular underpinnings of FASD-associated abnormalities is needed. To this end, we will test a novel mechanistic hypothesis that ethanol disrupts chloride homeostasis in embryonic neurons, and propose to assess the therapeutic potential of targeting chloride co-transporters in order to develop and advance strategies for the pharmacological intervention of FASD in utero. We propose two specific aims: Specific Aim 1: Test the hypothesis that bumetanide, an NKCC1 blocker, prevents or rescues in utero ethanol's effect on NKCC1-mediated chloride homoeostasis and mitigates the abnormal tangential migration. Specific Aim 2: Test the hypothesis that mPFC-dependent reversal learning is impaired in young adult mice exposed in utero to ethanol but not in those co-treated with bumetanide. Bumetanide is an FDA-approved drug that has been used therapeutically in humans as a diuretic agent in treatment of hypertension. More recently, prompted by the finding that GABA-induced depolarization may play a role in neonatal seizures, bumetanide treatment was shown to decrease epileptic events in rat models of hypoxic neonatal seizures and pilocarpine-induced temporal lobe epilepsy and is now in Phase 1 clinical trials for treating infants with hypoxic neonatal seizures. Encouraged by our own preliminary supporting data, our goal is to explore the effectiveness of bumetanide in preventing or rescuing the tangential migration defect and enduring neurobehavioral and cognitive impairment seen with in utero exposure to ethanol. An underlying goal is to minimize the risk to the fetus yet provide the desired benefit. Overall, NKCC1 will be pharmacologically targeted for the first time as potential therapy for the untoward effects of ethanol exposure on tangential migration, chloride homeostasis and long-term neurobehavioral and cognitive outcomes. We take a multi-level neuroanatomical, electrophysiological and behavioral approach to set the groundwork and inform future more comprehensive studies that will hopefully lead to clinical trials. The exploratory studies proposed are highly significant and innovative, high risk/high yield, with great potential for translational impact on the therapeutic management of FASD.